Giant enhancement of the initial SERS activity for plasmonic nanostructures via pyroelectric PMN-PT

Reversible Thermoelectric Regulation of Electromagnetic and Chemical Enhancement for Rapid SERS Detection

Actively controlling surface-enhanced Raman scattering (SERS) performance plays a vital role in highly sensitive detection or in situ monitoring. Nevertheless, it is still challenging to achieve further modulation of electromagnetic enhancement and chemical enhancement simultaneously in SERS detection. In this study, a silver nanocavity structure with graphene as a spacer layer is coupled with thermoelectric semiconductor P-type gallium nitride (GaN) to form an electric-field-induced SERS (E-SERS) for dual enhancement. After applying the electric field, the intensity of SERS signals is further enhanced by over 10 times. The thermoelectric field enables fast and reproducible doping of graphene, thereby modulating its Fermi level over a wide range. The thermoelectric field also regulates the position of the plasmon resonance peak of the silver nanocavity structure, rendering synchronous dual electromagnetic and chemical regulation. Additionally, the method enables the trace detection of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). A detailed theoretical analysis is performed based on the experimental results and finite-element calculations, paving the way for the fabrication of high-efficient E-SERS substrates.

Thermoelectrically Driven Dual-Mechanism Regulation on SERS and Application Potential for Rapid Detection of SARS-CoV-2 Viruses and Microplastics

Electric-induced surface-enhanced Raman scattering (E-SERS) has been widely studied for its flexible regulation of SERS after the substrate is prepared. However, the enhancement effect is not sufficiently high in the E-SERS technology reported thus far, and no suitable field of application exists. In this study, a highly sensitive thermoelectrically induced SERS substrate, Ag/graphene/ZnO (AGZ), was fabricated using ZnO nanoarrays (NRs), graphene, and Ag nanoparticles (NPs). Applying a temperature gradient to the ZnO NRs enhanced the SERS signals of the probe molecules by a factor of approximately 20. Theoretical and experimental results showed that the thermoelectric potential enables the simultaneous modulation of the Fermi energy level of graphene and the plasma resonance peak of Ag NPs, resulting in a double enhancement in terms of physical and chemical mechanisms. The AGZ substrate was then combined with a mask to create a wearable thermoelectrically enhanced SERS mask for collecting SARS-CoV-2 viruses and microplastics. Its SERS signal can be enhanced by the temperature gradient created between a body heat source (∼37 °C) and a cold environment. The suitability of this method for virus detection was also examined using a reverse transcription-polymerase chain reaction and SARS-CoV-2 virus antigen detection. This work offers new horizons for research of E-SERS, and its application potential for rapid detection of the SARS-CoV-2 virus and microplastics was also studied.